Abstract: Advantages and disadvantages of traditional determination method for mixing uniformity of fully mixed ration preparation machine were analyzed．Combined with requirements of ruminant feeding science on fully mixed diet, method of measuring mixing uniformity by using grading screen was proposed．Under the same conditions, two methods were used to test mixing uniformity of three grades of fully mixed ration preparation machine, such as good, average and poor. Results showed that mixing uniformity of the second and third layers of screening method could better represent operational performance and quality of fully mixed ration preparation machine．This method strengthened rationality of mixing uniformity data of fully mixed ration preparation machine, helped production enterprises and users to distinguish operation quality of fully mixed ration preparation machine, and provided reference for product upgrading and user purchase．